Single point injection carb replacement

[Paul H]

Best horsepower doesn't change at all between 12 and 13 afr and best lean hp is at 13.2afr so fuel distribution problems would have to be large to show up. If you tune at steady state aiming for 13.2afr and start loosing power at say 12.9 then you have a lean cyl and a fat cyl the lean cyl is loosing the power. In these tests I didn't notice anything odd

[Piledriver]

Best horsepower doesn't change at all between 12 and 13 afr and best lean hp is at 13.2afr so fuel distribution problems would have to be large to show up. If you tune at steady state aiming for 13.2afr and start loosing power at say 12.9 then you have a lean cyl and a fat cyl the lean cyl is loosing the power. In these tests I didn't notice anything odd

Logical conclusion.
I'd still suggest very good manifold heat on any center mount fuel source, even without a venturi...

[sideshow]

...itb-42-45idf compare.jpg...

Looking at that excellent graph (thanks for sharing), I suspect the choke point is in the end castings. Also there does seem to be some minor benefits the smaller the intake gets, maybe air velocity is more important than shear size.

Although the untold benefits of IR is how little throttle position they require to make great power everywhere. And far more peak power.

[Paul H]

...itb-42-45idf compare.jpg...

Looking at that excellent graph (thanks for sharing), I suspect the choke point is in the end castings. Also there does seem to be some minor benefits the smaller the intake gets, maybe air velocity is more important than shear size.

Although the untold benefits of IR is how little throttle position they require to make great power everywhere. And far more peak power.

Yes but you don't see the whole story on those graphs firstly the engine has quite large oval ports which I had to blank off with a plate to give stock port size as the end castings wouldn't cover them so if the engine had regular mild ported heads on a stock casting like most people have that work with something less than a "big beef" manifold you can wave goodbye to at least 10hp probably 15hp. Secondly the graphs are without belt and if you look at the other power graphs it shows the belt takes far more power at higher revs than at lower revs say an extra 8hp also now I remember the 130hp was with mufflers removed and 126hp with mufflers. So in the real world not that much difference for the IR-ITB combo

Logical conclusion.
I'd still suggest very good manifold heat on any center mount fuel source, even without a venturi...

Yes for sure but the exhaust I have doesn't have the heat takeoffs so can't test

[Piledriver]

....
Although the untold benefits of IR is how little throttle position they require to make great power everywhere. And far more peak power.

Actually you can make more power with a properly designed plenum (or airbox) ask BMW/AUDI...
You can probably even make more power with a single properly sized TB....and plenum, with much better throttle control, having effective WOT at low RPM be ~5% TPS is not a feature, although it FEELS really sporty.


Doing so on an upright cooled ACVW is another matter... The cooling system is very much in the way, and just sticking plenums over the carbs/ITBs on each side doesn't really work due to the firing order.

[Paul H]

We went from the largest to the smallest with very little change in hp/torque to 4500rpm so I doubt there is some magical mystery intake that will change that much and if you want max top end then ITB will always rule unless you are an oem car manufacturer with strict emission control in which case they would be a PITA

[Paul H]

ITB test done about a year ago - They get boring after a while

[sideshow]

Well since your in the testing mode, why not use a propane torch on the single TB at the tee? As long as the engine is running I doubt there is much hazard (sans moving parts) of directly heating the aluminum casting or the steel tube remains of the riser.

[Paul H]

We got a stock 1600cc to play with next carb v tb with heat risers in a few months though. For 1904cc engine it would be easier to fit a cam sync and fire injector into moving air stream less time for fuel to condense out but it's not causing any problems as it is so probably wont bother I only use the car in summer

[Paul H]

It keeps changing colour in here !
Doing some work on the 1904cc engine.
Changing the heads to stock 35.5x32 single HD springs with a port cleanup no enlargement or reshape.
New 1.5 OD header with heat risers
Doghouse cooler going back in and an OG fan housing.
CR will be increased and hopefully won't loose too much torque due to smaller valves

[paul_f]

Very interesting Paul!

[Paul H]

Videos disappeared with site overhaul.
Seems OK now

[Paul H]

Latest version
36mm tapered bore with direct mount 2 bolt fitment and OEM TPS

solex36.jpg

[Clonebug]

That is awesome Paul!!!!!

[Lanner]

Very nice Paul. Are you selling the TB?

Thanks
Lanner